The present invention relates to a gas etching method in which an object to be etched is etched by jetting an etching gas onto the object for etching, and a jetting nozzle used in such a gas etching method.
In order to etch an object such as a silicon wafer by using a gas, generally, the etching gas is activated by plasma or the like and, at the same time, the activated gas flow is controlled by electrodes or a magnetic force. However, in some cases, the silicon wafer, poly-silicon film and/or SiO2 film are etched by using only the etching gas.
In this case, regarding the etching method, as shown in FIG. 3, generally, an object for etching 101 mounted on a support 102 is entered into a reaction vessel 103. The reaction vessel is depressurized by evacuation through a discharge opening 104, and the etching gas is jetted for etching on a portion of the object to be etched from an end of an etching gas introducing pipe (nozzle) 105 for a predetermined time period.
The following formula (1) indicates only a typical chemical reaction of etching of silicon. The etching gas jetted from the end of the etching gas introducing pipe 105 is struck against the object for etching to form a reactant with the object which is gasified for effecting the etching.
Si+4F*xe2x86x92SiF4↑+C2F6xe2x80x83xe2x80x83(1)
In this case, excess gas for etching is discharged from reaction vessel 103 through discharge opening 104, as shown by the arrows in FIG. 3.
As mentioned above, although the excess gas is discharged from the reaction vessel 103 through the discharge opening 104, if a path to the discharge opening 104 is long, a portion of the object 101 other than the portion to be etched is also etched away, which is problematic. In particular, when an amount to be etched is great, such as several xcexcmxcx9cseveral tens of xcexcm, no problem would be caused. However, if the amount to be etched is small, such as several hundreds of xc3x85xcx9cseveral thousands of xc3x85, then, a great disadvantage will be caused.
The present invention is made in consideration of the above-mentioned problems, and an object of the present invention is to provide a gas etching method, a gas jetting nozzle and a gas etching apparatus which can eliminate the above-mentioned conventional drawbacks and in which only a portion of an object which is desired to be etched can be etched with high accuracy.
To achieve the above object, according to the present invention, there is provided an etching method for etching an object by jetting an etching gas onto the object from a gas jetting nozzle. A gas jetting pipe for jetting an etching gas and a suction or discharge pipe for discharging (evacuating) the etching gas jetted from the gas jetting pipe are provided. The gas jetting pipe and the suction pipe are designed to have a coaxial dual pipe structure and the etching gas is jetted from the gas jetting pipe toward the object for etching and, at the same time, excess etching gas is discharged through the discharge pipe.
The present invention further provides a gas jetting nozzle for jetting etching gas toward an object for etching, wherein a gas jetting pipe for jetting the etching gas and a suction (evacuating) pipe for discharging (evacuating) the jetted gas are provided. The gas jetting pipe and the suction pipe are designed to have a coaxial dual pipe structure.
In the gas jetting nozzle according to the present invention, in the dual pipe structure constituted by the gas jetting pipe and the suction pipe, one of the gas jetting pipe and the suction pipe is disposed on the inside, and the other of the suction pipe and the gas jetting pipe is disposed on the outside.
In the gas jetting nozzle according to the present invention, in the dual pipe structure constituted by the gas jetting pipe and the suction pipe, tip ends of both pipes are positioned flush with each other, or a tip end of one of the pipes protrudes outwardly from a tip end of the other pipe by a predetermined amount.
The present invention further provides a gas etching apparatus comprising a gas jetting nozzle according to any one of the arrangements stated above; a reaction vessel; and means for jetting an etching gas from a gas jetting pipe of the gas jetting nozzle onto an etching portion of an object positioned within the reaction vessel and, at the same time, for evacuating excess etching gas for reaction through the gas suction pipe.
As mentioned above, when the object for etching is etched by using the gas jetting nozzle having the dual pipe structure, only a portion for etching is etched, and the etching gas does not flow to a portion where etching is not desired, with the result that etching having a very sharp profile can be effected.
Therefore, according to the present invention, with the use of a gas jetting nozzle in which a gas jetting pipe and a suction pipe are designed to have a coaxial dual pipe structure, and by jetting the etching gas from the gas jetting pipe toward the object for etching and, at the same time, by discharging excess etching gas through the suction pipe, a gas etching method, a gas jetting nozzle and a gas etching apparatus in which only the portion of the object where etching is desired can be etched with high accuracy can be provided.
The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative examples.